There are two different ways to authorize a friend or relative to use your debit card. You can add the person to your account officially as an authorized user, or you can simply share your card and personal identification number informally, as many people do. From the bank's perspective, the first way is the right way and the second way is definitely the wrong way.
Sharing Your Card and PIN
If you want a friend or family member to pick something up at the store for you or to have access to money for some reason, you can give her your debit card and PIN so she can use the card. However, this could potentially be a big mistake if the person you gave the card to abuses your trust.
If you report an unauthorized charge no more than 60 days after the bank sends you your statement, you aren't liable for any charges according to the Federal Trade Commission. If you lose your debit card but report the loss to your bank immediately you are also protected.
However, if you voluntarily share your PIN with another person, you don't have any legal protection and can be held liable for all charges. If the person you gave your PIN to chooses to spend or take out more money than you authorized, the bank does not have to give it back to you.
If you check your bank's debit card agreement, you will most likely find that it is a violation of the agreement to share your card or PIN with anyone. The bank may also reserve the right to cancel your account.
Adding an Authorized User
If you want to let a friend or relative use your debit card without violating your card agreement, you can add that person to your account as an authorized user. Depending on your bank, you may be able to add a new user through online banking or over the phone, although some banks may require you to come in and fill out a form.
In most cases, the only information you need is the birth date, name and Social Security number of the person you want to add. He'll receive his own debit card, but the bill will still come to you. If you add an authorized user to your account, you'll still be responsible for any charges just as if you had shared your PIN. Depending on your bank's rules, you may be able to reduce your risk by setting a limit to how much the person is authorized to spend or withdraw.
You can also remove him from your account at any time just by calling your bank, and you won't have to worry that the bank will close your account for violating your cardholder agreement.
Letting someone else use your account is risky either way, and you should only take this step with someone you really trust.